This invention relates to a method of encapsulation which is reversible, that is, a method which may be used to encapsulate a liquid or a solid material and thereafter to release the material by selectively disrupting the capsule membranes. An important embodiment of the invention involves the microencapsulation of living cells which may subsequently be released from within the produced capsule membranes without damage.
U.S. Pat. No. 4,352,883 entitled "Encapsulation of Viable Tissue and Tissue Implantation Method," filed Mar. 28, 1979 by F. Lim discloses a microencapsulation technique which can be used to encapsulate essentially any solid or liquid material within semipermeable or substantially impermeable capsule membranes. An outstanding advantage of the process is that the conditions under which the capsule membranes are formed involve no toxic or denaturing reagents, extremes of temperature, or other conditions which damage living cells. The process of that application is accordingly well-suited for the production of microencapsulated living materials which remain viable and in a healthy state. Because the process allows a degree of control of the permeability of the membrane, it is now possible to microencapsulate cell cultures of procaryotic, eukaryotic, or other origin such that cells of the culture are protected from contaminating bacteria, high molecular weight immunoglobulins, and other potentially deleterious factors, and remain confined within a microenvironment well-suited for their continuing viability and ongoing metabolic functions. If the microcapsules are suspended in a conventional culture medium sufficient to support growth of the living cells involved, the microencapsulated cells are free to ingest substances needed for metabolism which diffuse through the membrane and to excrete their metabolic products through the capsule membrane into the surrounding medium.